Sunday, February 26, 2012

Can consultant's BIM Model be used for construction?

Can consultant's BIM Model be used for construction?

This is the popular question of last few months?

Let me give you some background information before going into the discussion. Especially in the UAE almost all the large consultants are already using BIM. Of course with different level of expertise and success. However compared to the contractors, consultants are BIM gurus:)

The consultant educates the client about BIM and recommends to mandate BIM usage in the tender. Client is happy because he thinks he already have the BIM Model so the contractor will only operate it.

The consultant hands over a LOD 300 model with no/limited liability.

The party starts here!

Contractor believes that he can use consultant's model for shop drawings, quantities, cost planning, scheduling etc.

I have experienced this myself. When we told the contractor that the model coming from consultant can not be used as it is, they do not want to believe and most of the time they do not believe.

Now, let's imagine a project in which the design consultant hands over a LOD 300 BIM Model. (If you are not familiar with LOD please check James Van's blog! It is pretty cool)

First of all, we should define what is LOD 300.

"LOD 300 - Model elements are suitable for the generation of traditional construction documents and shop drawings. As such, analysis and simulation is authorized for detailed elements and systems."

When a contractor reads the above statement, he is quite sure that the model will work fine for him. Unfortunately what a consultant understands from "shop drawings" is slightly different than contractor's understanding.

A basic example. A consultant can use a multi-story column might work fine for the shop drawings of a consultant but it should be from slab top to slab bottom in contractors model.

The consultant does not care about the concrete grades but for contractor it is very important.

Even for design coordination! Many people believes that clash detection within a LOD 300 model is perfect. But not really! In a complex project, the slight difference on the radius of the bend might create a clash in LOD 400 model where LOD 300 is absolutely ok!

What do we usually recommend for contractors?
If the consultant does not accept "full" liability on the model, do not rely on it.

Freeze the consultant's design model as a reference model and create your own. You might create your own model by just modifying and developing the design model but we saw cases in which it is much easier to create the model from scratch. So evaluate both options.